CHAPTER 6: Derivatisation for Direct Infusion– and Liquid Chromatography–Mass Spectrometry

The concept of derivatisation to enhance the ion signal is almost as old as biological mass spectrometry (MS) itself. In this chapter we will concentrate our attention on derivatisation methods to enhance ion signals in desorption ionisation methods, primarily matrix-assisted laser desorption/ionisation (MALDI) and electrospray ionisation (ESI), both for direct-infusion (DI)-MS and liquid chromatography (LC)-MS. Derivatisation provides advantages in lipidomics, as besides enhancing ion current can add specificity in terms of both solution chemistry and gas-phase ion chemistry via the collision-induced dissociation (CID) process. There are downsides to derivatisation methods, namely in terms of added complexity and time in sample preparation and the often unavoidable issues raised by excess derivatisation reagent and side reactions. As such, derivatisation methods tend to be exploited in groups with a chemistry background; however, the availability of reagents in kit format should facilitate the use of these methods by MS groups in general.